Spatiotemporal Analysis of Long-term Air Pollution in Two Urban Regions of Vietnam and Potential Source Contributions

Abstract

Vietnam is one of the fastest urbanizing and industrializing countries in Southeast Asia, yet long-term and spatially integrated air quality assessments remain scarce due to limited ground-based observations. Previous studies have focused mainly on short-term measurements in Hanoi or Ho Chi Minh City, without providing a national-scale comparison or integrated source apportionment across both regions. Reanalysis products such as Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA2) are increasingly available, their application for long-term evaluation of multiple pollutants (CO, SO₂, BC, and PM₂.₅) in Vietnam has not been systematically performed.Our study addresses these critical gaps by (i) analyzing a 43-year dataset to reveal spatiotemporal trends and seasonal variability, (ii) comparing MERRA2 reanalysis against U.S. Embassy and Consulate observations to assess model performance in the Vietnamese context, and (iii) applying Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model combined with Potential Source Contribution Function (PSCF) and fire hotspot analysis to disentangle the relative roles of local emissions, industrial zones, and transboundary biomass burning. By doing so, this work not only advances scientific understanding of Vietnam's air pollution dynamics but also provides a robust baseline to support evidence-based policy design, cross-border collaboration, and the country's net-zero emission pathway.